4) If an ROC citizen is married to an alien, where should they file income tax returns?

Source: Taipei National Tax Administration, Ministry of Finance Last Update: April 16, 2008

If they choose to file a joint return ( no matter whether the alien is
resident or non-resident ) and choose the ROC citizen to be the taxpayer, they
can file their income tax returns with the tax authorities located in the
district where they live, or they may file at the Foreign Taxpayers Office of
the National Tax Administration if they choose the alien to be the taxpayer.
Those residing in Taipei City should file taxes at the Foreign Taxpayers
Section, Taipei National Tax Administration, at No. 2, Sec. 1, Jhonghua Road, Taipei City. However, no matter where they file tax returns, their income should be filed jointly.